SCCF Contributes to Hawksbill Research in Virgin Islands
The endangered hawksbill sea turtle (Eretmochelys imbricata) could be facing climate-related stressors at one of the species’ biggest nesting sites in the U.S. Virgin Islands, suggests a study led by Sabrina Sorace, former SCCF sea turtle intern and current master’s student at the University of the Virgin Islands.
SCCF Coastal Wildlife Director and Sea Turtle Program Coordinator Kelly Sloan has kept a close working relationship with Sorace and is serving on her master’s committee for the research.
The Caribbean is home to approximately half of the global hawksbill nesting population, and Sorace’s research took place at Sandy Point National Wildlife Refuge (SPNWR) in St. Croix, where hawksbill nesting activity has been increasing at 4.5% per year since 2003.
Sorace and her team analyzed hawksbill hatch success at SPNWR from 2020 to 2023, nest incubation temperatures from 2021 to 2023, and nest water content for the peak 2023 nesting season. SCCF graciously lent 30 sets of data loggers to measure temperature and moisture.
Nest incubation temperatures were used to predict hatchling sex ratios and investigate the relationship between sand temperature and hatch success.
The results suggest that hawksbill nests at SPNWR mainly produced female hatchlings during peak nesting season (June to October) from 2021 to 2023. Several nest temperatures were also over 34°C (93.2°F) during peak 2023 season. This is the temperature expected to produce equal numbers of each sex for hawksbills, and also the maximum temperature before nests tend to exhibit lower hatch success.
Hawksbill nests incubating outside of the peak season had lower average temperatures, suggesting seasonal differences in the survival and sex ratios of hawksbill hatchlings. There was also wide variation in the moisture content of nests.
“These findings suggest that as climate change progresses, provided nesting seasons don’t shift, hawksbill hatchling production in the Caribbean may decrease and should continue to be monitored,” the authors conclude.
Sorace said her time at SCCF ultimately led her to this work.
The internship “truly jumpstarted my passion for investigating how the environment influences the embryonic development of sea turtles and how resource managers can adapt conservation strategies to respond to a changing climate,” she said.
SCCF Sea Turtle Program Coordinator Kelly Sloan said Sorace’s preliminary results are another example of the need for sustained sea turtle conservation efforts.
“Increases in nesting, such as those seen locally on Sanibel and Captiva or in SPNWR, are encouraging, but sea turtles continue to face many threats at each life stage — and not just in Florida,” she said. “Research initiatives constantly aim to shed more light on sea turtles’ responses to these threats, but it’s clear that monitoring and research remain critical even in the face of record nest counts.”
Sanibel and Captiva Islands normally only see nesting loggerhead and green sea turtles, and on rare occasions, leatherbacks and Kemp’s ridleys.
In addition to the St. Croix Sea Turtle Project, other contributing institutions include the U.S. Fish and Wildlife Service, The Ocean Foundation, the National Save the Sea Turtle Foundation, and the Lana Vento Charitable Foundation.